Magnetotail reconnection following a flapping motion of the magnetotail on 17 July 2017

We report a magnetotail reconnection event observed by MMS on 17 July 2017. The event was preceded by multiple magnetic field fluctuations due to flapping of the magnetotail as indicated by repeated changes in the sign of thexcomponent of the magnetic field. MMS and Cluster, respectively located in the pre-midnight and post-midnight sectors, observed current sheet flapping that propagated away from the midnight sector. Significant tailward outflow jets appeared immediately after the initial fluctuation of the flapping motion, suggesting that flapping may have an effect on reconnection. During the period of tail flapping, MMS was located in the exhaust region tailward of an X-line. The flapping motion enabled MMS to probe the northern and southern sides of the exhaust and separatrix regions, repeatedly. MMS then moved past the X-line region from tailward to earthward, detecting strong electron jets along the dawnward direction, crescent-shaped electron distribution functions, dissipative signatures, and enhanced electron vorticities. Using this unique event, we investigate 1) the relationship between the tail flapping and magnetotail reconnection, 2) sub-layers of the exhaust region, as indicated by particle distribution functions and different wave modes, as a function of distance both along and normal to the current sheet, 3) the electron diffusion region for magnetotail reconnection with a moderate guide field (B_g 0.3B₀), and 4) multiple wave modes coexisting at the separatrix.